The proton motive force is the energy generated from transferring protons or electrons across an energy-transducing cell membrane. The energy is then used to perform chemical, osmotic or mechanical work.
The proton motive force exists in eukaryotes and prokaryotes. In eukaryotes, it is located across the inner mitochondrial membrane and is generated by energy from the citric acid cycle. The proton motive force is used to make ATP from ATP synthase. In plants, the proton motive force is located in the thylakoid membrane of chloroplasts. The force is generated by the light reaction during photosynthesis. It is used to make ATP, which is used in the fixation of CO2.